Always repeating $PMTK010 and $PMTK011 commands

[sainath]

I use GPS (FGPPM0PA6B) which consists of MTK chipset. I am having a strange problem. Once I switch on the  GPS on my system which is battetry powered (3.3V) for sometime I start getting the weird $PMTK010 and $PMTK011 commands again and again as you can see it from the screenshot attached. What might be the possible source of error. I have read previously that these commands are given out when the GPS has finished its boot up process, but why does it hangs there, repeating the same sequence again and again.

Thank you for reading

Regards
Sainath

[Horsa]

Repeating $PMTK010 and $PMTK011 commands mean that the PA6B GPS module is repeating power on/off.
Would you please provide the following items for us:

• description or photo of test environment
• schematic diagram of the base board
• photo of base board

Do you have the opportunity to monitor power supply voltage with an oscilloscope?

[sainath]

Thank you Fabio for your apt reply.

I am using a Power distribution switch TPS2092 to switch on and off the GPS. They are always on. The VCC of the TPS2092 is the output of a DC-DC converter MCP1640 i.e output is 3.3V, I could see sometimes the ripples in my oscilloscope at the VCC of the GPS. But few other times even though there is no ripple, after sometime it starts emitting this PMTK commands.

Regards
Sainath

[Horsa]

Please send us your schematic diagram and baseboard picture.
Please send us your part number and firmware version.
Please verify carefully power supply and signal levels: even short voltage drops can force the module to reboot.

Without further information, the only thing we can recommend you is to

• remove TP2029 and MPC1640
• connect Vcc and Enable pin of PA6B directly to 3.3 V power supply

Then please let us know the result.

[sainath]

As you have said, I have used  USB power to drive the GPS and it works well, as I have seen keeping a Switch Mode Power Supply, I believe the inrush current is low when I am using a battery cell, but the main problem is that I have to use GPS in a battery powered system. So that is the main reason for using DC-DC boost converter (MCP1640) and power distribution (TPS2092) switch to switch off the GPS.

[sainath]

No reply yet, I have done the experiment which you have told its working well with an external supply.

Regards
Sainath

[Horsa]

This proves that the GPS module PA6B (Globaltop FGPPM0PA6B) itself works correctly. This confirms that the problem is the system in general and most probably the power supply chain in particular.
How to get your system up an running now? You have typically two options: a) improve your circuit or b) re-design your circuit.

a) improve your circuit
Extend your power supply chain one component at a time, carefully monitoring all parameters of the power supply. I would start adding first the Microchip MCP1640 (Step-up DC/DC Regulator) and then the TI TPS2092 (power distribution switch).

b) re-design your circuit
That really depends on your full specifications.

Again, it is impossible for us to help you further if you do not provide us with the information required in our previous replies.

[sainath]

Thank you Horsa ,

I am attaching the schematic here. Please have a look at it. I will also try to do what you have suggested regarding connecting individual components.

Regards
Sainath

[Thorsten Trenz]

Hi,
you need a 100nF ceramic capacitor directly at the GPS module. Depending on your layout, you need even larger capacitors at the module

best regards
Thorsten Trenz